1,2,3,4-Tetrachlorohexafluorobutane is an important compound as a raw material or the like for synthesis of hexafluoro-1,3-butadiene that is attracting attentions as an etching gas for use in fine processing of semiconductors. As a process for producing this 1,2,3,4-tetrachlorohexafluorobutane, a process described in the following patent document has been heretofore known.
In Japanese Patent Laid-Open Publication No. 2006-342059 (patent document 1), a process for producing 1,2,3,4-tetrachlorohexafluorobutane by allowing a compound represented by CClX1X2—CClX3—CClX4—CClX5X6 (X is a hydrogen atom or a fluorine atom) to react with fluorine in the liquid phase. In the patent document 1, it is described that in this process, perfluoroalkanes, perfluoroethers, perfluoropolyethers, chlorinated hydrocarbon and perfluoroalkylamines are used as solvents. In the patent document 1, it is also described that use of 1,2,3,4-tetrachlorohexafluorobutane as a solvent for fluorination reaction is particularly preferable because there is an advantage that separation between the solvent and the product is unnecessary. In this process, however, the reaction raw material is diluted with the solvent and fluorination reaction is carried out in a low concentration, so that a problem remains with regard to production of a desired product industrially economically and efficiently.
By the way, in the process in which an organic compound and fluorine gas are allowed to directly react with each other in the absence of a catalyst, it is usually an important point how efficiently and unwastefully expensive fluorine gas is used, in order to economically produce the desired product. In the patent document 1, however, utilization rate of the fluorine gas has not been studied at all.
Also from this viewpoint, therefore, the process for producing 1,2,3,4-tetrachlorohexafluorobutane described in the patent document 1 leaves a problem with regard to production of a desired product industrially inexpensively and efficiently.
It is known that isomers such as optical isomers are present in the 1,2,3,4-tetrachlorobutane. When it is used, without distinguishing between the isomers, in the form of a mixture of isomers as a diluent or a solvent, the reaction temperature is frequently set on the basis of an isomer having a high melting point among the isomers. Therefore, in the case where liquidphase reaction is carried out, the reaction temperature must be occasionally set at a high temperature of certain degree in order to perform reaction while keeping a liquid state. If the reaction is carried out in this way, there occurs a problem that, for example, side reaction to form a low-boiling component proceeds because of cleavage of C—C bonds in the fluorination reaction to thereby lower yield of the desired product or the fluorination reaction proceeds excessively.
Accordingly, in addition to how to utilize the fluorine gas effectively as described above, how to prepare the desired product in a high yield is also a problem to be solved.